Device for reversing fan blades



y 21, 1957 K. A. DAGRELL 2,792,897

DEVICE FOR REVERSING FAN BLADES Filed July 10, 1952 i this axle.

2,792,897 DEVitCE FOR REVERSING FAN BLADES Kraut Airs Dagrell, .lonkoping, Sweden, assignor to A B Svenska Flaktfahriken, Stockholm, Sweden Application .iuly 10, 1952, Serial No. 298,163 tllaims priority, application Sweden July 13, 1951 1 Claim. (Cl. fill-160.4)

The present invention relates to a device for the reversing of revolving fan blades mounted along the circumference of an impeller, which fan blades are supported about an axle and revolve by means of an arm radially projecting from the axle mentioned.

in propeller fans it is known per se to construct the impeller with varying forms of the separate fan blades. It is also known per se to shape the fan blades with an elliptic section. It is also in use with fan blades having an acute form reckoned towards the one edge side. In certain cases as in drying plants, ventilating devices and the like, the propeller fan must often work in different directions in order to reverse the current of medium. The present invention relates to a reversing device for propeller fans.

The invention is substantially characterized by a disk supported on an axle having the same centre as the rotating axle of the impeller but entirely separated from The disk is provided with holes along its circumference in order to engage pins perpendicularly projecting from the ends of the radial arms mentioned, which pins are directed towards the disk mentioned. The disk is axially slidable and is driven by rotation of the impeller by means of a rod which is mounted in the impeller and coaxial with its rotating axle. Means are arranged for an axially sliding of the mentioned disk and a driving of the mentioned pins in order to effect a reversing of the blades during the rotation of the impeller.

According to a convenient embodiment said means consist of a screw fastened to the axle of the disk, which screw is arranged to move the disk axially along the rod by means of a worm wheel co-operating with a wheel engaged with the screw.

The sliding disk driven by the fan is according to a. modification arranged in a recess of the impeller. Other characteristics of the reversing device will appear from an embodiment of the invention more fully described in the following as an example.

Fig. 1 is a section of the impeller having a reversing device.

Fig. 2 is a quarter of the impeller having a reversing disk and a connection between the fan blades and the driving disk.

In Fig. 1 a fan blade is designated 16, the bearing pin 15 of which consists of an axle supported by the bearings 12, 13, and 14 mounted in the outwardly extending axial peripheral flange of an impeller 6b. Each axle of the fan blade is provided with a radially projecting arm 11. This arm 11 is provided with a pin 10 ecccntrically arranged at its external end and said pin is provided with a shank terminating in an enlarged ball-shaped extremity or knob 9. Each knob rests in a recess 9a conforming to the outline of the pin 10 in a radially extending lobe on the periphery of a driving disk 7 which comprises a generally circular plate having an axial dimension greater than the diameter of said ball-shaped extremities. The driving disk 7 is by means of a hub-like member reposing within the flange of the impeller on a bearing 4 on an axle 3a having the same centre as the rotating driving shaft 3 6a of the impeller but entirely separated from this shaft. The hub-like member 5 is placed at such a distance from the shaft 6a that the axle 3a can be displaced to and fro along the common centre line without striking the rotating shaft 6a of the impeller. A screw 3b is fastened to the axle 3a, which screw can be displaced by means of a worm 1 co-operating with a worm wheel 2 engaged with the screw to and fro along the common centre line, when driving the bearing 4, the hub-like member 5 and the driving disk 7 fastened to this member. The driving disk 7 is thus forced to move to and fro along a pin 8 in parallel with the rotating shaft 6a of the impeller. The hub-like member 5 is freely rotatable in relation to the axle 3a by means of the bearing 4. The driving disk 7 can therefore by means of the guide-pin 8 be forced to rotate together with the impeller 6b about the shaft 6a and at the same time a desired position in relation to the impeller can be effected by moving the driving disk axially (in parallel). When moving to and fro, the pin 10 and knob 9 of each fan blade will follow the movements of the driving disk, whereby the arm 11 will turn the bearing pin 15 of the fan blade in a position corresponding to an intended adjustment of the fan blade or fan blades.

The invention refers to the possibility of reversing the fan blades during the rotation of the impeller entirely independently of this rotation.

I claim:

For a fan having a driving shaft, an impeller mounted at one extremity of said shaft, and having an axial peripheral flange extending outwardly therefrom, and a plurality of radially disposed fan blades mounted in circumferentially spaced relation on said impeller flange for pivotal rotation on their axles, means to vary the pitch of said blades comprising a crank arm extending radially from each axle, a pin rigidly mounted on each crank arm and extending radially inward of said impeller flange and disposed parallel to said axle, said pins having shanks terminating in enlarged ball-shaped extremities, a disc coaxial with said impeller within said flange and consisting of a generally circular plate having an axial dimension greater than the diameter of said ball-shaped extremities and a plurality of radially extending lobes corresponding in number to the number of fan blades, means defining in each lobe a recess of uniform key-hole cross-section corresponding to the outline of said. pin, an axially movable nonrotatable screw axially aligned with said driving shaft in spaced relation beyond the driving shaft, a hub rotatably mounted on said screw for axial movement therewith and extending inwardly toward said impeller, said hub mounting said disc, a rod mounted in said impeller axially slidable in said disc to connect said disc to said impeller for rotation therewith, and means for axial adjustment of said screw and said disc to pivotally displace said crank arms and said fan blades comprising an internally threaded worm wheel engaged on said screw and a worm for driving said worm wheel to effect axial displacement of said screw.

References Cited in the file of this patent UNITED STATES PATENTS 1,181,458 Iskols May 2, 1916 1,837,568 Moody Dec. 22, 1931 1,857,392 Nixon May 10, 1932 1,869,280 Roemisch July 26, 1932 1,887,045 Schwarz Nov. 8, 1932 2,054,810 Gaba Sept. 22, 1936 2,241,008 Turna May 6, 1941 2,348,249 Ferro May 9, 1944 2,428,128 Sheppard Sept. 30, 1947 FOREIGN PATENTS n-nulra- IaIl-n n 

